Archaeologists have found 34,000 year old stone tools with blue paint residues in the Caucasus. It is the earliest evidence of artifacts with the plant dye indigo. Accordingly, people use the leaves of the Färberwaids in a targeted manner in terms of the old stone time in order to crush them with pebbles and to gain the blue color from them. This throws a new light on Homo sapiens’ sophistication – even if it is still unclear what our ancestors used the color for.
The plant isatis Tinctoria L., also known as the dyeberwaid, has long been used for dyeing jeans and other fabrics because of its dye indigo. Other ingredients of this plant with a health -promoting effect are used in medication. The blue molecule indigotine arises when the vacuoles of the plant cells are destroyed by grinding or grinding, with precursor molecules (indoxylglycosides) released, which then react with the atmosphere. These plant properties took advantage of the Egyptians millennia ago. But when did people discover this dye and when did you specifically extract the indigo from the plants for the first time?
Stone tools from the Caucasus
Surprisingly provides information on this from Georgia. Archaeologists had recovered stone tools in the Dzudzuana cavity in the foothills of the Caucasus in the 2000s. These tools are between 32,000 and 34,000 years old, as dated the surrounding layer of rock showed, and come from Stone Age residents of the cave. A team led by Laura Longo from the University of Venice has now examined the six unprocessed pebbles under the microscope in order to learn more about their function.
It was shown that the Stone Age people once used these smooth tools to shred soft and moist material such as leaves and minerals. The archaeologists also found remains of blue fibers and starchy grains on the visibly worn stone parts. These blue remains are the dye indigo, as different spectroscopic analyzes revealed. The color was created by the molecule indigotine, also called indigo, which can also arise from the leaves of the colored waid.
Coloring traces from the Paleolithic period
But when and how did the color come on the stone tools? Was it an oversight or were the relics specifically used for color production? In order to find out, the researchers examined the pores contained in the stones using synchrotron radiation and micro-computed tomography. These tests showed that the pores are large enough to capture organic remains. This suggests that the paint residues were not only superficial, but through intensive use to the pores of the stones – which is why they have been preserved to this day.
The team then replaced the stone tools and thus carried out a number of experiments with dyeing waid plants. To do this, they collected corresponding pebbles from the Nikrisi river below the Dzudzuana cave as raw material. From this they made several pounding and sanding tools and crushed and grinded with them by hand leaves from Isatis Tinctoria. The material generated in this way compared them with the traces on the tools found in the cave.
Targeted use of plants as raw materials
These experiments confirmed that 34,000 years ago, people in the Caucasus used stone tools to crush leaves from the dyeing waid domestic there and to gain the dye indigo from them. The vegetable color was therefore already known in the old stone and was used in a targeted manner. It is the oldest evidence of this behavior to date.
Since Färberwaid is bitter and not edible, the finds also confirm that the Homo sapiens recognized 34,000 years ago that some inedible plants are also suitable as raw material. “Instead of only considering plants as food resources, the Homo sapiens converted the perishable materials into products for everyday life 34,000 years ago,” says Longo. “Our approach opens up new perspectives on the technological and cultural sophistication of the young Paläolithic populations, which skillfully exploited the inexhaustible resource of the plants and were fully aware of the power of the plants.”
Whether the Stone Age people used the indigo for coloring clothes or for wall paintings, other plant substances made of dyeberwaid for medical purposes or both is not evident from the finds. However, the blue plant color could have significantly expanded the palette of the then common mineral dyes such as ocher, red, yellow, black and white.
Source: University of Venice; Specialist articles: Plos One, DOI: 10.1371/Journal.pone.0321262
